the radial, the angular
and the spin part
\begin{equation}
\psi(r,\theta,\phi,\sigma ) =
{1\over r} P_{n\ell}(r)Y_{\ell m_{\ell}} (\theta,\phi)
\chi_{m_{s}}(\sigma).
\end{equation}%%                                                  %   10
The $Y_{\ell m_{\ell}}$'s are spherical harmonics